Abstract: Based on the survey data in polyculture pond system of Gracilaria tenuistipitata v. and Penaeus monodom in Lian′an town Haifeng county Guangdong province, China from April 2002 to September 2003, a neuro-fuzzy system model was developed to describe the non-linear relationships among the biological and physicochemical factors in pond in different growth phase of Penaeus monodom. The model simulated the theoretic lowest growth rate of Gracilaria tenuistipitata v. in different growth phase of Penaeus monodom within the eutrophication restrict criteria of dissolved nitrogen in water DIN≤0.2 mg·L^-1. The simulated results well reflected the effect of actual growth rate of Gracilaria tenuistipitata v. on the DIN in polyculture pond system.